Myocardial contractile function and the cardiac sympathetic system are impaired when ventricular hypertrophy and congestive heart failure result from pressure overload on the heart. Little is known of the potential for recovery of contractile function and myocardial catecholamine stores following relief of the pressure overload. Even less is known of factors which may determine the potential for recovery of contractile function and catecholamine stores or of possible avenues for recovery. The research project for which this supplemental support is requested has as its goal the study of isolated tissue from an experimental animal model of reversible pressure overload induced ventricular hypertrophy and congestive heart failure in an attempt to provide: (1) Knowledge of the extent to which contractile function will recover following relief of pressure overload hypertrophy and congestive failure and an understanding of the factors which may determine the reversibility of this contractile defect. (2) Knowledge of the extent to which the depletion of cardiac catecholamine stores is reversible following relief of pressure overload and an understanding of the factors which may determine irreversibility. (3) Exploration of the possibility of ameliorating or preventing these defects or enhancing their reversibility by administration of digitalis at the initiation of and during the pressure overload stress. During the first year of investigation approximately one third of these goals have been achieved and the remaining goals are being actively pursued. However, a pressing practical need for additional personnel to properly complete these goals has become increasingly apparent as a result of the experience in the initial studies. These needs are similar to those requested for support in the original grant application. Further, the initial results have provided new answers, which have in turn generated unexpected closely related additional areas for fruitful investigation into the mechanisms underlying the initial results. This supplement is requested to provide the needed support for full pursuit of the remaining goals and simultaneous study of the newly apparent aspects of this project.